There is much interest in improving the fuel economy of gasoline and diesel engines. This can be done, through the lubricant engine oil, by reducing the friction contribution either of the bulk fluid (by lowering the oil viscosity) or improving the friction of the contacting parts by inclusion of friction modifier additives.
There is therefore interest in additives with low friction properties in low viscosity oils.
Dispersant viscosity modifier (DVM) additives are known to provide friction modification. Examples known in the art, based on polymer technology, are olefin copolymers (OCP) and methacrylate copolymers. A problem with such additives especially in applications which require ultra-low viscosity lubricating fluids such as OW-8, OW-16, OW-20 is their high thickening efficiencies.
Poly(2-oxazoline)s are known in the art. For example, the art describes the living cationic ring-opening polymerization of 2-oxazolines. See Hoogenboom et al., Angew. Chem. Int. Ed 2009, 48, 7978-7994. U.S. Pat. No. 4,120,804 describes the use of short oligomers of poly(2-oxazoline)s (number of repeating units (n)=2-15) as a dispersant to prevent or reduce the formation of sludges, or to neutralise acidic components etc. in lubricating oils. The polymerisation initiator is a polymeric material of molecular weight equal to or greater than 250 and the oxazoline is 2-substituted with a hydrocarbyl group of 1-18 carbon atoms. No mention is made of friction modification, or of lubricant viscosity impact.